Support setlocale via CONFIG operation. (#11059)

Till now Redis officially supported tuning it via environment variable see #1074.
But we had other requests to allow changing it at runtime, see #799, and #11041.

Note that `strcoll()` is used as Lua comparison function and also for comparison of
certain string objects in Redis, which leads to a problem that, in different regions,
for some characters, the result may be different. Below is an example.
```
127.0.0.1:6333> SORT test alpha
1) "<"
2) ">"
3) ","
4) "*"
127.0.0.1:6333> CONFIG GET locale-collate
1) "locale-collate"
2) ""
127.0.0.1:6333> CONFIG SET locale-collate 1
(error) ERR CONFIG SET failed (possibly related to argument 'locale')
127.0.0.1:6333> CONFIG SET locale-collate C
OK
127.0.0.1:6333> SORT test alpha
1) "*"
2) ","
3) "<"
4) ">"
```
That will cause accidental code compatibility issues for Lua scripts and some
Redis commands. This commit creates a new config parameter to control the
local environment which only affects `Collate` category. Above shows how it
affects `SORT` command, and below shows the influence on Lua scripts.
```
127.0.0.1:6333> CONFIG GET locale-collate
1) " locale-collate"
2) "C"
127.0.0.1:6333> EVAL "return ',' < '*'" 0
(nil)
127.0.0.1:6333> CONFIG SET locale-collate ""
OK
127.0.0.1:6333> EVAL "return ',' < '*'" 0
(integer) 1
```

Co-authored-by: calvincjli <calvincjli@tencent.com>
Co-authored-by: Oran Agra <oran@redislabs.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/redis.conf b/redis.conf
index 13b29c428..3bb52e76d 100644
--- a/redis.conf
+++ b/redis.conf
@@ -409,6 +409,11 @@ set-proc-title yes
 #
 proc-title-template "{title} {listen-addr} {server-mode}"
 
+# Set the local environment which is used for string comparison operations, and 
+# also affect the performance of Lua scripts. Empty String indicates the locale 
+# is derived from the environment variables.
+locale-collate ""
+
 ################################ SNAPSHOTTING  ################################
 
 # Save the DB to disk.